Process for the commercial production of di-calcium phosphate



Jan. 13, 1931. A. HOLZ 1,788,952

PHOCESS'FOR THE COMMERCIAL PRODUCTION OF DI-CALCIUI PHOSPHATE Filed April 21. 1927 sugmur maml zzc felqim ll kslls 5111726? Na CZ +17 0 Rock firma'a Rock P/zasp/zafe Feactzan VesseL filte fbr Ca 50 lime Burn:

filler for Ca //P04 INVENTOR v, 1-' A ATTORNEY Patented Jan. 13, 1931 AUGUST HOLZ, OF IRVINGTON,

i mean NEW JERSEY, ASSI GN OR TO THEODORE VQD. BERD ELL,

OF NEW YORK,'1\T. Y;

rnoonss non 'rnn COMMERCIAL PRODUCTION oF n'I-cALcIu rnosrnn'rE Application filed April 21,

This invention relates more particularly to the commercial production, in a continuous process, of di-calcium phosphate by electrolytic treatment of alkali-metal chlorides, so

i as to utilize certain of the products to produce di-calcium phosphate by treating tricalcium phosphate.

Di-calcium phosphate is a compound, Which owing to its neutral character, nonhygroscopic qualities and high available phosphoric acid contents Would form a very valuable fertilizer if it could be produced at a low enough cost to compete With ordinary commercial fertilizers.

In my pending applications, Serial No. 91,819, filed March 2, 1926, and Serial No.- 135A89, filed September 14%, 1926, I have disclosed novel methods of producing di-calcium phosphate electrolytically; In both methods,

however, it is necessary to re-combine the liberated hydrogen and chlorine-in order to obto bring about the union of chlorine with hydrogen in a much more economical Way, which leaves the electrolytically obtained hydrogen as a by-product, available for other purposes, as for instance, the synthesis of am- I moma.

In practicing my process, as herein described, and as illustrated by the accompanying flowsheet, I electrolyze a solution of cominercial alkali-metal chloride, for instance sodium chloride, by means of an electric current. During such electrolysis chlorine Will be liberated from the anode, While at the cathode -the alkali-metal ions Will combine with the Water, formingalkali-metal hydroxides and liberating hydrogen.

As six molecules of chlorine are necessary for the decomposition of every molecule of tri-calcium phosphate-Which, as rock phosphate, is the raw material of my processthe 1927. Serial No. 185,867. folloxvingequation indicates the reaction 6Nao1+currene 6o1+611+cNa0H, r

' The liberated gases hydrogenand chlorine are collected separately. The hydrogen, as

previously indicated, is of high purity and therefore available for other purposes, for ln'stance, for the synthesis of ammonia. The

chlorine gas, however, is passed into Water, nto which an equivalent amount of sulphur dioxide gas is fed simultaneously. Both gases, bymutual reaction in' the presence of Water, form hydrochloric and sulphuric acids, according to the following equation cc1 +aso,+cngosenci rangsor 'This'mixune r hydrochloric and sulphuric I acids is noiv'allovved'to act on crude rock phosphate (tri-calcium phosphate) 'accord-, mg to the following equation 6I Io1+eH,so,+2o i,P,o

' 3CaCl5+3CaSO The insoluble-calcium sulphate is then removed by filteration, and to the filter-ate are now added one molecule of calcium'hydroxide and six molecules of alkali-metal hydroxide,

or'the sodium hydroxide produced electro lytically, as previously described. This results in the formation of insoluble di-cal cium phosphate and the regeneration of th electrolyte sodium chloride as shown by thefollowing equation acaonfin ro; +01 (0H) (iNaOH-e The insoluble di-ca lciuin'phosphate'may be formed also Without the use of calcium hydroxide. For example, When sodium hydroxide is added to the filtrate, thefollowing reaction takes place: I

The insoluble di-calcium phosphate of this arm. I

last reaction is removed by filteration and the mother liquor containing the alkali-metal chloride is aga n ready for electrolysis, which may be repeated as prevlously described.

Instead offproceeding as'given above, the

solution of 3CaCl +lH PO may be concentrated and then allowed to act on one more molecule of Ca-QP O according to the followin equation:

.CaCl elH PO Ca P O If to this solution the six molecules of sodiulnhydroxide are added,'t.he insoluble diin the last named filtrate is treated with calcium hydroxide and sodium hydroxide.

This specification signed and witnessed this 19th day of April, 1927.

AUGUST HOLZ.

alcinm phosphate Will be precipitated and the electrolyte sodium chloride is regenerated as shown by the following equatlon:

3CaCl 30111-1 110 6NaOH GCaHPO 6NaCl 61-1 0.

The insoluble di-calcium phosphate of this last reaction is removed by filtration as before and the mother liquor is then ready for electrolysis, and thus repeat the process coninuously. I The equations given above represent the main reactions, but it Will be understood that I do not Wish to confine myself to the exact equivalents mentioned therein, for small mounts of impurities in the crude rock-may necessitate a slight adjustment, but this Will ing the chlorine and an equivalent amount of sulphur dioxide into Water to produce a mixture of hydrochloric, and sulphuric acids, reating tri-calcium phosphate With said acid mixture, removing the calcium sulphate resulting from the last reaction, by filtration. then treating: the filtrate with a solution of alkali-metal hydroxide, thereby producing dialcium phosphate and regenerating the alkali-metal chloride.

2. The commercial process for the 0011- v tinuous production of di-calcium phosphate, which comprises electrolytically decomposing .n alkali-metal chloride solution to produce hydrogen, chlorine and a solution of the alkali-metal hydroxide, simultaneously passine'the chlorine and an equivalent amount isulphur dioxide into water to produce a mixture of hydrochloric and sulphuric acids,

' treating tri-calcium phosphate with said acid mixture, to produce calcium chloride, calcium sulphate and phosphoric acid, removing said alcium sulphate by filtration, then treating the filtrate with said electrolytically formed alkali-metal hydroxide, thereby producing dicalcium phosphate and restoringthe original alkali-metal chloride. r

3. The process as claimed in claim 2, Where- 

